The Earth is not entirely solid, there is liquid rock core in the center. This liquid core is probably where Earth gets its Magnetic Field. This magnetic field, in turn, blocks solar wind and other harmful radiation. The liquid nature of its core is apparently the cause of seismic activity in the surface.
The Earth's atmosphere is 71% Nitrogen, 21% Oxygen, and the rest being other gases such as Carbon Dioxide. The planet's plant life is a major source of the Oxygen. This is one of the major reasons why environmentalists protest against the destruction of tropical rainforests for timber and other resources.
About three-fourths of the surface of Earth is covered with water. It is able to exist in three states-solid, liquid, and gas-thanks to adequate temperatures maintained on Earth. Water is said to be essential to the formation of life.
With this abudance of liquid water and other necessary chemicals we see a plethora of life on Earth. Earth life forms vary from the microscopic bacteria, to the tall redwood trees, to the enormous Blue Whale. Among these life forms are the intelligent bipedal animals known as humans.
Humans are a peculiar life-form. With the intelligence and ability to manipulate objects with their hands, they have transformed the planet. They developed technology and culture. Their technology has aided in creation, quality of life, death, and destruction. Technology has built wonderous things like cities and temples and has helped improved the lives of people, but it is also used to destroy them too.